Ineffective delivery of transplanted cells to the desired site is a major hurdle hampering the clinical application of cell-based, regenerative medicine therapies. Dismally low transplanted cell viability (~1-32%) is caused both by the mechanical forces during injection, which damage the cell membrane, and the lack of a three- dimensional matrix to support cell survival in situ. Peripheral arterial disease (PAD), occurs to one in 20 Americans over the age of 50. Current treatment options are often ineffective, commonly leading to amputation in cases of critical limb ischemia. A promising therapy is the transplantation of patient-derived human adipose- derived stromal cells (hASCs) into the ischemic site to promote reperfusion through secretion of pro-angiogenic paracrine factors. Here we propose a physically-crosslinked, double-network hydrogel with a wide range of stiffness from 10 to 3000 Pa to address the problem of post-transplantation cell death, to regulate cell functionality to optimize the angiogenic potential of hASCs, and to improve blood reperfusion in a murine model for PAD. In Specific Aim 1, I will synthesize and characterize an injectable hydrogel that undergoes two different physical crosslinking mechanisms. The first crosslinking step occurs ex vivo through peptide-based molecular recognition to encapsulate cells within a physical hydrogel, while the second crosslinking step occurs in situ through a thermal phase transition to form a reinforcing network. This hydrogel will be formulated with a wide range of stiffness from 10 to 3000 Pa by varying the reinforcing network densityto provide hASCs protection during syringe injection and to improve the cell viability post-transplantation. In Specific Aim 2, I will explore the effect of stiffness on the secretion of pro-angiogenic growth factors by hASCs in vitro and maximize the angiogenic potential of hASCs encapsulated within this series of novel hydrogels. In Specific Aim 3, I will choose the best-performing hydrogel formulation and deliver hASCs to a murine hind limb ischemia model of PAD. Recovery of blood perfusion and neovascularization will be assessed to validate the hASC-based therapy using our novel hydrogels, seeking to accelerate the clinical realization of cell therapy for PAD.